The purpose of this application is to acquire training and develop expertise in the application of the mathematical techniques of genetic modelling to the study of the genetics of those psychiatric disorders that begin in childhood. The discovery of specific genetic influences on the development of psychiatric disorders of childhood can facilitate early diagnosis and prevention, and broaden understanding of the contributions of both nature and nurture to the development of psychiatric illness. But psychiatric disorders are in general phenotypically complex, and can be expected to exhibit genotypic complexity as well. Genetic modelling of complex disorders requires (a) attention to possible violations of modelling assumptions by data, (b) the evaluation of the implications of such violations for the analysis of data, and (c) the incorporation into the models of appropriate corrections for substantive violations of modelling assumptions. The candidate, an applied mathematician with extensive training in genetic epidemiology and the epidemiology of psychiatric disorders of childhood and adolescence, proposes to acquire additional training in human genetics and specific mathematical techniques of genetic modelling, required for a fruitful research career in genetic modelling of psychiatric disorders of childhood. Training will be provided through course work at Columbia Univ. and UCLA; formal tutorials; work in the Columbia University linkage laboratory; and ongoing consultation with a panel of distinguished advisors. Research will be conducted on the application of mathematical models to the genetic epidemiology of early-onset major depression, panic disorder, and Tourette syndrome. Initial research will concentrate on the development, extension, and evaluation of modelling methods for the assessment of genetic heterogeneity within these disorders.